// Simple infinite horizontal scroller.

// Press Left/Right to speedup/slowdown change direction etc.
// Just an experimental demo made available to illustrate the technique.

// by James Shaughnessy james@manc.u-net.com
// http://www.netyaroze-europe.com/~shaughnj


#define MAXSPEED 50                     // Max scroll speed pixels/frame

#include <stdio.h>
#include <libps.h>

#include "pad.h"


extern DISPENV GsDISPENV;

void DrawPicture();

main()
{
  u_long PadStatus = 0;

  RECT left, right;
  short offset = 0, inc = 0;

  // Setup graphics PAL
  SetVideoMode(MODE_PAL);
  GsInitGraph(320, 256, 4, 0, 0);
  GsDISPENV.screen.y = 20;
  GsDISPENV.screen.h = 256;

  GsDefDispBuff(0, 0, 0, 0);

  PadInit();

  DrawPicture();


  // Permanently set variables
  left.x = 0;
  left.y = 256;
  left.h = 256;
  right.y = 256;
  right.h = 256;

  while(1)
  {
    PadStatus = PadRead();

    // Quit if both Select and Start pressed
    if (PadStatus & PAD1select && PadStatus & PAD1start) break;

    if (PadStatus & PAD1Lleft)
      if (inc > -MAXSPEED) inc--;
    if (PadStatus & PAD1Lright)
      if (inc < MAXSPEED) inc++;

    // Set rects
    left.w = offset;
    right.x = offset;
    right.w = 320 - offset;


    // Wait for a vertical blank
    VSync(0);

    // Copy virtual screen parts to visible area
    MoveImage(&right, 0, 0);
    if (offset)                                 // Only if non-zero; avoids
      MoveImage(&left, 320 - offset, 0);        // zero width rect copy

    DrawSync(0);
    GsSwapDispBuff();

    // Increment offset (scroll!) and set to legal value
    offset += inc;
    if (offset >= 320) offset -= 320;
    else if (offset < 0) offset += 320;
  }

  ResetGraph(0);
}




// Draw a picture on the screen
// (50 Random rectangles)
void DrawPicture()
{
  RECT scr;                                    // Virtual screen
  RECT box;
  int i;

  scr.x = 0;
  scr.y = 256;
  scr.w = 320;
  scr.h = 256;

  ClearImage(&scr, 0, 0, 0);

  for (i=0; i < 50; i++)
  {
    box.x = rand()%290 + scr.x;
    box.y = rand()%226 + scr.y;
    box.w = 10 + rand()%30;
    box.h = 10 + rand()%30;
    ClearImage(&box, rand()%256, rand()%256, rand()%256);
  }
}












// ****** PAD routines ******
// low-level pad buffers: never need to touch
volatile u_char *bb0, *bb1;

// call once only in program initialisation
void PadInit (void)
{
  GetPadBuf(&bb0, &bb1);
}

// call once per VSync(0)
// puts controller pad status into unsigned long integer
// please refer to the manuals if you want explanation 
// of the internals of this function
u_long PadRead(void)
{
  return(~(*(bb0+3) | *(bb0+2) << 8 | *(bb1+3) << 16 | *(bb1+2) << 24));
}